1. Field of the Invention
The present invention generally relates to a wideband high frequency bandpass filter, in particular to a wideband high frequency bandpass filter utilized to filter the electromagnetic wave having a central frequency of 60 GHz.
2. Description of the Related Art
The Federal Communication Commission of Unite States on 2011 established a standard that any wireless communication at the band near 60 GHz (i.e. 57-64 GHz) enjoys the right of using free band width, and thus international major communication companies such as LG, Panasonic, NEC, Samsung, Sony and Toshiba promote that high resolution videos without compression but with resolution up to 1920×1080 p can be wirelessly transmitted at the band of 60 GHz. In high frequency transmission, 60 GHz can thoroughly implement wireless communication and high speed transmission in our daily life.
Wherein, the filter can determine the frequency range of transmission signal, and thus designing a bandpass filter filtering the electromagnetic wave with a central frequency of 60 GHz becomes the researching emphasis in recent years.
It is worth to mention that bandpass filters have been already developed maturely in conventional Wi-Fi technology. Thus, the research and development personnel starts developing the bandpass filter applying on filtering the electromagnetic wave with a central frequency of 60 GHz based on the bandpass filter developed in Wi-Fi technology. However, the signal frequency which the bandpass filters developed in accordance with the broadly used Wi-Fi technology are able to handle fall within the range of a few GHz and hundreds of MHz. Consequently, the conventional designing standard of bandpass filter in Wi-Fi technology will be hard to achieve well performing bandpass filter having the central frequency of 60 GHz.
More specifically, the transmission distance is confined owing to the severe power absorption in the air of the 60 GHz signal. Thus, all the currently available 60 GHz bandpass filters can not achieve low loss, high conversion efficiency and broad stopband extension, and using the designing methology of the conventional bandpass filter will require more elements and leads to higher design complexity and higher cost.